Apparatus and method for controlling tape speed and tape pack formation in a high speed tape transporter

ABSTRACT

As tape moving at high speed through a closed loop tape transporter (10) is conveyed into a storage bin (64) the tape is directed against a curved tape deflecting surface opposite and in spaced-apart relation to the bin entrance (63). A plurality of vacuum ports (96) are positioned in spaced-apart relation generally along the path of tape movement on the tape deflecting surface (64A). As the tape moves along the tape deflecting surface (64A), vacuum-induced drag is applied to the tape to create a progressive breaking force which slows the tape and causes the tape to form into loops. The loops assist the tape is accumulating in the bottom of the bin in a controlled manner.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates generally to the high-speed movement of tapewhere tension and speed control are critical factors. The particulardisclosure of this application is a closed loop, high-speed tapetransporter of the type used to duplicate audio signals off of a rapidlymoving master tape onto tape at at least one slaved duplicator.

This process is carried out by passing a closed loop of recording tapeacross a pick-up head where a signal on the loop of tape is conveyeddownstream to the slaved duplicator. The loop of tape is conveyed fromthe pick-up head into a storage bin for accumulation while a trailinglength of the loop of tape is passed across the pick-up head. The loopcontinues endlessly from the bin back across the pick-up head, with eachcomplete passage of the loop across the pick-up head providing acomplete replication of the signal from the loop which is conveyed fromthe pick-up head to the slaved duplicator.

Typically, a relatively large number, such as ten, slaved duplicatorsare connected to a single tape transporter of the type described above.Hence, each complete passage of the master tape through the transporterresults in ten copies being made. Eventually, these copies are loadedinto cassettes for use in tape playback devices.

Tape duplicating processes are subject to a number of industry-imposedstandards. A world-wide standard cassette playback speed has been set at17/8 inches per second (ips) 4.76 centimeters per second (cps) for manyyears. All speeds at which the tape is processed must therefore bereferenced in some manner to this standard. Historically, this hasrequired difficult trade-offs between tape processing speed and tapeplayback quality. As is well known, the higher the recording speed, thegreater the fidelity and playback quaility which is obtained. At onetime, the tape duplicating industry recorded master tapes at 7.5 ips (19cps), thereby achieving a very high quality standard. However, in aneffort to increase efficiency and output, the duplicating industry beganduplicating at 64 times normal speed. However, to reproduce at 64 times7.5 ips (19 cps) would mean a master tape speed of 480 ips (1219 cps).This was found to be impossible to achieve on a commercial basis, sincethe master tapes very quickly broke or wore out and, in addition, theplayback quality of the duplicated tape was very poor. Therefore, inorder to maintain the 64 to 1 ratio, the master recording speed was cutin half to 3.75 ips (9.5 cps), thereby permitting a 64 to 1 duplicatingratio at a master tape speed of 240 ips (610 cps). When 3.75 ips (9.5cps) was adopted as standard master recording speed, this was acceptablebecause cassette tape and duplicating slaves were not capable ofproducing quality sufficient to take advantage of higher recordingspeeds. However, with the advent of new types of tape, improvedrecording heads, more sophisticated electronics and the development ofDolby HX Pro high frequency headroom extension system, it became clearthat recording the master at 3.75 ips (9.5 cps) constituted a strictupper limit on the quality which could be achieved. Repeated attempts toincrease the duplicating speed to 480 ips (1219 cps) has resulted ininefficiencies caused by frequent master tape replacement and poorplayback quality. Many of these attempts have involved increasing thespeed of the tape transporting capstans in an attempt to simply move themaster tape more rapidly through the transporter. However, the physicalaffects of moving a relatively thin tape at ever increasing speeds arenot always linear or even predictable. Experience in the design of tapetransporting devices has shown that many different variables controllingtape movement must be controlled and improved to achieve operatingefficiency combined with high frequency amplitude stability, highfrequency phase stability, and an enhanced stereo image on the endproduct cassette tape.

The invention described in this application permits a master to berecorded at 7.5 ips (19 cps), and duplicated at a 64 to 1 ratio whilesubstantially improving the efficiency of the tape transporter and thequality of the cassette tape.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a method andapparatus which permit tape to be transported through a tape transporterat higher speeds with greater reproduction fidelity;

It is another object of the present invention to provide a method andapparatus which reduces the speed of travel of a tape as it enters atape bin of a high speed tape transporter;

It is yet another object of the invention to provide a method andapparatus for preventing damage to a master tape as it enters the bin ofa high speed tape transporter;

It is still another object of the invention to provide a method andapparatus for forming a regular pattern of loops in a tape as it entersthe bin of a high speed tape transporter and accumulate those loops inthe bin in a relatively compact, uniform mass.

These and other objects and advantages of the present invention areachieved in the preferred embodiment disclosed below by providing in aclosed loop, high-speed tape transporter vacuum supply means, a tape bindefining a tape deflecting surface opposite and in spaced-apart relationto an entrance through which the tape enters the tape bin and againstwhich the tape is propelled. A plurality of vacuum ports are provided invacuum flow communication with the vacuum supply means and arepositioned in spaced-apart relation generally along the path of tapemovement of the tape deflecting surface to apply a progressive breakingforce to the tape as it enters the bin. The tape speed is slowed and thetape is caused to form loops as it moves along the tape deflectingsurface. The loops assist the tape in accumulating in the bin in acontrolled manner.

According to the preferred embodiment of the invention, the tapedeflecting surface comprises a curved surface which begins at an angleacute to the direction of tape movement into the bin and ends at anangle generally perpendicular to the angle of tape movement into thebin. Preferably, the vacuum ports are equally spaced-apart and define awidthwise dimension less than the width of the tape whereby the vacuumports are completely covered as the tape moves along the tape deflectingsurface.

In the method according to the present invention, a structure isprovided which defines a tape deflecting surface against which the tapeis propelled. A plurality of vacuum ports are provided in spaced-apartrelation generally along the path of tape movement on the tapedeflecting surface to apply a progressive breaking force to the tape asit is propelled against and along the tape deflecting surface, to slowthe tape speed sufficiently to cause the tape to form loops as it movesalong the tape deflecting surface.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the descriptionof the invention proceeds when taken in conjunction with the followingdrawings, in which:

FIG. 1 is a perspective view of a tape transporter according to thepresent invention, in combination with a plurality of slavedduplicators;

FIG. 2 is a front elevational view of the tape transporter of the typeshown in FIG. 1;

FIG. 3 is a view of the tape transporter in FIG. 3, showing thethreading pattern while loading the master tape;

FIG. 4 is a view of the transporter shown in FIG. 2, with the tapeloaded for duplication;

FIGS. 5, 6 and 7 are schematic views showing the tension and speedcontrol function of the vacuum columns on the tape transport;

FIG. 8 is a schematic view of the pneumatic control circuit whichcontrols the vacuum ports in the tape bin;

FIG. 9 is a schematic view of the vacuum guide roller;

FIG. 10 is a schematic view of the pneumatic pinch roller controls;

FIG. 11 is a schematic view of the pneumatic vacuum holdback and pullforward functions of the vacuum columns;

FIG. 12 is a cross-sectional view of the crowned capstan rolleraccording to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings, a closed loop high-speedtape transporter according to the present invention is shown in FIG. 1and broadly indicated at 10. Tape transporter 10 comprises a cabinetenclosure 11 within or on which all of the working parts of transporter10 are contained. As can be seen, all of the tape manipulating portionsof transporter 10 are contained on a vertically extending front panel12. A vacuum supply 11A, a microprocessor-based controller 11B and allother auxiliary equipment are contained in cabinet 11 behind front panel12. Tape transporter 10 is electrically connected to a series of slaveunits "S." Each slave unit reproduces the program on the endless mastertape onto, for example, audio cassette tape and winds the audio cassettetape onto a large reel, usually referred to as a "pancake" which is thenloaded onto a cassette loader. The cassette loader takes a "C-O"cassette, extracts the leader, cuts the leader and splices one half ofthe leader onto the leading end of recorded audio tape on the pancake,winds a single reproduction of the program recorded from the master tapeinto the cassette, then splices the trailing end of the audio tape ontothe second half of the cassette leader, ejects the cassette and thenrepeats the process.

BRIEF DESCRIPTION OF TAPE HANDLING COMPONENTS

Referring now to FIG. 2, front panel 12 of tape transporter 10 includesa control panel 13 having a display 14 and switches 15-23, inclusive,the functions of which are described below. A lockable hub 25 driven bya motor 26 is positioned in the lower left hand corner of front panel 12and is used only when loading a tape. Freewheeling guides 28-33,inclusive, are positioned in predetermined spaced-apart relation onfront panel 12 and cooperate with other tape contacting surfaces toestablish the proper path of the closed loop of tape. A pair of opticalsensors 35 are positioned intermediate tape guides 29 and 30 and asimilar pair of optical sensors 36 are positioned near guide roller 32.The tape path extends between these two respective pairs of sensors 35and 36 and prevent operation of the tape transporter if the tape isimproperly threaded.

A vacuum column 40 is positioned on the lower half of front panel 12immediately above hub 25. Vacuum column 40 includes a back wall 41 whichincludes a sensing slot 42 which senses the vacuum pressure withinvacuum column 40 at any given time. In addition to back wall 41, vacuumcolumn 40 is defined by outwardly extending, spaced-apart side walls 43and 44, a bottom wall 46 and a transparent cover (not shown). Vacuumports 47 in bottom wall 46 communicate with a vacuum supply to exert avacuum force in vacuum column 40. The depth of side walls 43 and 44, andbottom wall 46 is essentially the same as the width of the tape.Therefore, when tape is in vacuum column 40, it defines an upper vacuumcolumn zone in communication with atmospheric pressure, and a lower,enclosed vacuum column zone defined by the tape and the lower portion ofthe side walls 43 and 44 and bottom wall 46. The lower zone, which issealed against communication with atmospheric pressure by the tape,communicates with vacuum supply through vacuum ports 47.

Another vacuum column 50 is positioned in the upper half of front panel12 and includes a back wall 51, outwardly extending, spaced-apart sidewalls 52 and 53, a bottom wall 54 and a transparent cover (not shown).Vacuum pressure is exerted on vacuum column 50 by vacuum through vacuumports 57. A sensing slot 58 is provided in back wall 51.

Vacuum column 50 operates in the same manner as vacuum column 40.Further details concerning the operation of vacuum column 40 and 50 areset forth below.

Tape transporter 10 includes four motor driven capstans. Capstan 60 ispowered by a synchronous electric motor 60A which runs at a constantspeed at all times during the tape duplication process. The onlyfunction of capstan 60 is to move the tape at a precise and constantspeed. A pinch roller assembly 61, which includes a hard rubber pinchroller 62 rides on the surface of capstan 60 and the tape therebetween.A capstan 62 is positioned downstream of vacuum column 50 and at anentrance 63 to a tape storage bin 64. Capstan 62 is driven by aservo-controlled motor 62A which is coupled to sensing slot 58 andvaries the speed of capstan 62 to maintain the loop of tape in areference position within vacuum column 50. A pinch roller assembly 65,including a hard rubber pinch roller 66, rides on the surface of capstan62.

A capstan 70, controlled by a servo motor 70A coupled to vacuum column40 is positioned above exit 71 from bin 64. A pinch roller assembly 73,including a hard rubber pinch roller 74, cooperates with capstan 70.

Tape is delivered to capstan 70 by a vacuum guide roller 76.

A capstan 80 is driven by a variable speed motor 80A and is positionedin the bottom of tape bin 64 and drives a low speed flat belt 81. Belt81 is positioned in driving relation between two rollers 82 and 83. Belt81 is driven counterclockwise and moves the pack of tape loops fromright to left and, at the same time, inverts the tape pack so that tapeis being removed from the top rather than the bottom of the pack.

As the tape is pulled through the exit 71 of bin 64, dampening belts 85and 86 eliminate a significant amount of tape flutter and preventstwisting of, and possible damage to, the tape as it exits tape bin 64.

Bin 64 is approximately the same thickness as the tape and includes siderails 64A and 64B to guide the tape downwardly. The upper portion of bin64 is covered by a glass door 86 mounted on hinges 87 and 88. Vacuumports 96 are positioned along side rail 64A in tape contacting position.The lower portion of bin 64 is enclosed by a glass door 90 which ispivoted on hinges 91 and 92. As can be seen by continued reference toFIG. 2, a vacuum chamber 94 is positoined adjacent bin 64 and includes avacuum port 95. Vacuum chamber 94 communicates with bin 64 and exerts avacuum pull on the lower extent of tape bin 64.

Finally, a reproduce head 100 is positioned between guide rollers 30 and31. As tape passes across reproduce head 100, the analog signal on themagnetic tape is sensed and transmitted by suitable electrical circuitrydownstream to the plurality of slaved tape duplicators "S."

PROCEDURE FOR LOADING MASTER TAPE INTO BIN

Referring now to FIG. 3, a master tape "T" which is stored on a suitablysized reel is placed on lockable hub 25. Motor 26 rotates in a clockwisedirection and therefore provides a holdback tension on the master tape,allowing it to ride over guide 28. The operator pulls the tape to theleft of guides 28 and 29, between optical sensors 35 and to the right ofguide 30. Sensors 35 detect the presence of the master tape beforeallowing transporter 10 to start its motors. This reduces the risk ofoperator error in misthreading the master tape. Sensors 35 also signalthe controller 11B when the end of the master tape has passed guideroller 29. Controller 11B stops the loading process whenever the tape isnot between sensors 35.

The tape is next threaded to the left of guide 31 and between capstan 60and pinch roller 67. Upper door 86 of tape bin 64 is opened and theoperator pulls the tape between capstan 62 and pinch roller 66 and downthe outside rail 64A and bin 64. Then, the bottom door 90 is opened andthe operator pulls the tape under the bottom of the inside rail 64B ofbin 64 and up through dampening belts 85 and 86. The tape is advancedabout four or five feet more before doors 86 and 90 are closed. The tapeis then passed to the left of and over vacuum guide roller 76 to theright of and over capstan 70 and over and to the left of guide 33 andthen down into the vacuum column 40, where the leading end of the taperesides during loading.

Switch 15 is then placed in the "low" position, switch 16 engages pinchrollers 67 and 66 with capstans 60 and 62 respectively. Switch 17 turnson the vacuum blowers. As soon as the vacuum pressure is at the correctlevel (3-5 seconds) the operator threads the section of tape betweencapstans 60 and 62 down into vacuum column 50. Switch 18, the "start"switch, is pressed and the controller 11B carries out a number of systemchecks. Transporter 10 will not start if capstan 60 is spinning, sincethis might damage the tape. Likewise, if the tape is not between sensors35, the transporter 10 will not start since this indicates amisthreading of the tape.

Once all test conditions have been met, capstan 62 begins turning.During the first four seconds, capstan 62 is rotated slowly to removeany slack in the tape path between hub 25 and capstan 62, except for thecorrect amount of tape in vacuum column 50. As is illustrated in FIG. 5,this amount is detected by a column transducer 55 which detects thevacuum in column 50 through slot 58. The column transducer 55 generatesa voltage to a servo circuit 56 which is proportional to the vacuumlevel within column 50. Servo circuit 56 controls the speed of motor62A. As the tape is pulled higher within vacuum column 50, the pressurebecomes more negative. When the pressure reaches a preset value, thetape is correctly positioned in vacuum column 50.

Once this condition has been achieved, full power is applied to capstan60 and the tape is pulled off of hub 25 and is allowed to drop intovacuum column 50. The servo circuit 56 controlling capstan 62 sensesthis level change and rotates capstan 62 clockwise at a speed sufficientto remove the same amount of tape as is being added to vacuum column 50by capstan 60. This process continues until the tail end of the tapepasses from between sensors 35 and the sensors are no longer blocked.

At any point during this loading operation, the operator may stop theprocess by pressing switch 19.

As the tape leaves capstan it 62, is forced to project outwardly in astraight line by a slight curve which has been introduced into the tapeby a crowned surface on capstan 62. (See FIG. 12). This eliminates theneed for knife-like strippers near the point of tape departure atcapstan 62. The tape is moving at 480 ips (1219 cps) during most of theload cycle. As noted above, this is the same speed at which thetransporter 10 operates during the duplication cycle. This is necessaryto insure that the tape packs in the bin 64 in the same manner as itwill while running in service.

The tape is allowed to contact the upper section of the 74A bin rail ata distance of approximately five to six inches (12.7-15 cm) from capstan62. This rail is made of stainless steel and is polished to preventscratches in the tape oxide surface. This rail also performs anotherfunction in that it decelerates the tape before it packs in the bottomof tape bin 64, as will be explained further below. It is important thatthis deceleration occur. If the tape is allowed to impact the pack inthe bottom of bin 64 at full speed, a number of problems result. Thepack does not form in a manageable fashion and tape forms such largeloops that it occupies too much space and the bin 64 will not hold longlength programs. The high impact may also damage the surface of the tapecausing loss of fidelity in the final product and premature replacementof the master tape. For this reason, the vacuum ports 96 are connectedto a high capacity low level vacuum source. As the tape passes the ports96, the vacuum progressively impedes the progress of the tape along therail slightly in relation to the tape which has not yet hit the firstvacuum port 96. This causes the tape to form loops. The vacuum level isquite low and the tape is merely slowed somewhat, but not stopped. Asthe moving tape passes across the successive vacuum ports 96, it formsprogressively larger loops as it descends. As is shown in FIG. 4, theloops decrease in frequency and increase in amplitude as they descentinto the bottom tape bin 34. Not only is the tape protected by slowingit somewhat, but the formation of the loops by vacuum ports 96 assistthe tape in falling into bin 64 in an even, regular pattern of loops.

While bin 64 is being filled with tape, belt 81 is driven at a slowspeed by capstan 80, as described above, so that the pack of tape isinverted, permitting tape to be removed from the bin during the run modewithout being pulled from the bottom of the pack where it is under highpressure due to the weight of the tape above it.

During the loading process, the controller 11B monitors the speed ofmotor 26. Because the speed of the tape is held at a constant 480 ips(1219 cps) by the constant speed of capstan 60, the rotational velocityof motor 26 continues to increase as the diameter of the reel of tapedecreases. At a predetermined velocity, which indicates the end of thetape is approaching, controller 11B reduces the average powertransmitted to capstan 60 and the tape slows to approximately 200 ips(508 cps) during the last few hundred feet.

When the end of the tape passes through sensors 35, the controllerdisengages the pinch rollers 67 and 66 from capstans 60 and 62respectively, and removes power from motors 60A, 62A, 70A and 80A. Thisallows the tail of the tape to be pulled down into vacuum column 50 andheld there by vacuum.

Finally, the operator removes the two ends of the master tape fromvacuum columns 40 and 50, respectively, and applies a splice, thusmaking the tape a continuous closed loop. Ordinarily, the spliceincludes a short section of transparent tape which forms a "window"through which sensors 35 and 36 can see as the tape completes eachcircuit. This "window" is used to generate a cueing signal which isapplied to the tape being reproduced at the slave duplicators "S" sothat the end of a particular program segment can be detected.

PROCEDURE FOR RUNNING MASTER TAPE

After completing the loading procedure, the tape must be threaded in aslightly different path. Referring now to FIG. 4, the vacuum supply 11Ais left on and the tape is allowed to drop into vacuum column 40 and 50.The tape exits the left side of vacuum column 40 and passes to the leftof guide roller 29 through sensors 35 and to the right of guide roller30. The tape is placed in front of the reproduce heads and to the rightof guide roller 31. The tape must then be placed to the left of guideroller 32 through optical sensors 36 and between capstan 60 and pinchroller 67. the tape is then placed between pinch roller 66 and capstan62.

At the exit 71 of tape bin 64, the tape passes between dampening belts85 and 86 and clockwise around vacuum holdback guide 76 which directsthe tape into capstan 70. The tape passes between capstan 70 and pinchroller 74 in a counterclockwise direction and over guide roller 33. Thetape drops into vacuum column 40, completing its circuit.

To start operation, the operator sets switch 15 to the "run" mode,closes switch 16 to engage pinch rollers 67 and 66 with capstans 60 and62, respectively, and checks switch 17 to insure that the vacuum supplyis still operating. By pressing switch 18, the controller 11B checks tomake sure that capstan 60 is stationary. It is important to make surethat capstan 60 is not rotating before tension is applied to the tape,since this may cause the tape to skew off of capstan 60. Frequently,this damages the edge of the tape.

Both sets of sensors 35 and 36 must indicate that tape is blocking lighttransmission, thereby insuring that the tape has been properly threaded.

Upon starting, the controller applies low power to capstan 60. Byrotating clockwise, capstan 60 removes slack from the tape path betweenvacuum column 40 and vacuum column 50. After a predetermined period,pinch roller 67 is engaged and capstan 60 is slowly accelerated. Capstan60 pulls the tape across the reproduce heads 110 while the vacuumpressure in vacuum column 50 is pulling the tape from the right side ofcapstan 60 into vacuum column 50. The change in position as the tapeenters vacuum column 50 is sensed by the vacuum transducer 55 which, asexplained previously, results in an increase in rotational velocity ofthe servo motor 62A controlling capstan 62. The increase in velocity ofcapstan 62 pulls the tape upward in vacuum column 50 until anequilibrium is established. Any amount of tape supplied to vacuum column50 by capstan 60 is removed by capstan 62. Therefore, the level of tapein vacuum column 50 remains relatively constant. Compare FIGS. 5, 6 and7.

In a similar fashion, as capstan 60 removes tape from vacuum column 40,the change in position of the tape is sensed by vacuum tranducer 48associated with vacuum column 40 which results in an increase in therotational velocity of servo motor 70A controlling capstan 70. Theincrease in velocity pulls tape out of bin 64 at a greater rate anddelivers it to vacuum column 40 until equilibrium has been established.Compare FIGS. 5, 6 and 7.

In the case of both vacuum column 40 and vacuum column 50, the "servo"aspect of the operation means that the speed of capstans 70 and 62,respectively, is varying constantly as the loop of tape moves upwardlyand downwardly within vacuum columns 40 and 50. Under idealcircumstances, the loop of tape would intersect sensing slots 42 and 58and define a reference position at its approximate mid-point. See FIG.5. Capstan 70 would deliver exactly the same length of tape per unit oftime to vacuum column 40 as is being withdrawn by constant speed capstan60. Likewise, capstan 62 would withdraw exactly the same length of tapeper unit of time to vacuum column 50 as being delivered by constantspeed capstan 60. The extent which tension variatios within tape bin 64vary from the ideal determines the extent to which the loop withinvacuum column 40 changes position and, consequently, the extent to whichthe speed of capstan 70 is varied to always try to put the loop of tapeback in the reference position at the approximate mid-point of sensingslot 42.

As is apparent, the primary purpose is to deliver the master tape acrossthe record heads at a precise and uniform tension. However, once thetape passes the reproduce head 100, tension control on the tape ceasesto be the primary object, and control of the speed of the tape becomesthe factor over which primary control is sought. This is because capstan60 is designed to rotate at a fixed speed of 480 ips (1219 cps), andmust maintain this speed as closely as possible.

Therefore, the primary purpose of capstan 62 and vacuum column 50 is toexert a "pull forward" tension on the tape which ideally exactly matchesthe holdback tension exerted by vacuum column 40. Motor 60A is relievedof the duty of pulling against the holdback tension created by vacuumcolumn 40. With the tension the same on both sides of capstan 60,capstan 60 can be devoted strictly to free running at a constant speed.Since the tape at the point between capstan 60 and pinch roller 67 isisolated on both sides from tension variations, there are no extraneousforces to cause even minute changes in the instantaneous rotationalvelocity of motor 60A. In fact, vacuum columns 40 and 50 functiontogether so well that surface speeds of up to 700 ips (1778 cps) atcapstan 60 have been achieved with little, if any, degradation inreproduction quality.

As the tape enters bin 64 through bin entrance 63, the tape lightlyglazes the outside rail 64A and decelerates by the action upon it ofvacuum ports 96, as described earlier.

Still referring to FIG. 3, the pack of tape can be seen in the extremebottom portion of tape bin 64. As the tape settles into the bottom ofbin 64, air is removed from between the layers of tape by a suctionthrough vacuum port 95. By removing air from between the layers of tape,a reduction in pack height is achieved which effectively increases thecapacity of the bin 64. Another effect is that the tape does not slideover the top of the pack upon initial contact. This results in loopsthat fit the bin from one end to the other and which are more manageablethan long loops which extend up the sides and are subject to tangling.

The transfer belt 81 is a low coefficient of friction tape having verylittle surface area in contact with the pack. Belt 81 is driven bycapstan 64 and moves in a slow, continuous motion causing the pack toinvert itself. The inversion allows the tape to be removed from the bin64 under very low tension because it is taken from the top of the pack.The speed of capstan 80 and consequently belt 81 is setsemi-automatically by the transporter controller 11A. The longer themaster tape, the slower belt 81 must move. Manual control can beeffected by means of a potentiometer 22 which causes a linear change inthe speed of capstan 80. Manual override by means of rheostat 22 is mostoften needed because of variations in the type of tape, temperature andhumidity which alter the packing characteristics of the tape.

Capstan 70 rotates in a counterclockwise direction pulling tape out ofbin 64 through bin exit 71. As tape is pulled off of the top of thepack, loops are formed. These loops are the result of unevenacceleration and it is common for sections of the tape to obtainvelocities well above 480 ips (1219 cps). The dampening belts 85 and 86therefore are set to contact any loop which may jump upward, therebyabsorbing some of the energy. Left undampened, loops having a largeamplitude may twist and even destroy the master tape.

Vacuum guide 76 supplies a holdback tension to the back surface of thetape. Vacuum guide 76 is quite large and the area affected iscorrespondingly large to reduce the wear on any given section of thetape and to reduce the change in tension if a small section were to losecontact with vacuum guide 76 momentarily. The vacuum level applied tovacuum guide 76 is adjusted such that the tape tension between vacuumguide 76 and capstan 70 is slightly less than the tape tension betweencapstan 70 and vacuum column 40. This nearly balanced tension allowspinch roller pressure applied by pinch roller 74 to be very low, furtherreducing wear on the master tape.

Tape leaving capstan 70 is pulled by vacuum column 40 across guideroller 33 and down into vacuum column 40.

By careful reference to vacuum columns 40 and 50, and followingcarefully the threading pattern of the tape through both vacuum columns,it will be seen that one side of the tape is in the inwardly facingposition of the lower vacuum column zone of vacuum column 40, and theopposite side of the tape is in vacuum communication within the lowervacuum column portion of vacuum column 60. The vacuum applied to theopposite sides of the tape results in a thorough cleaning of loose oxideparticles and dust from both sides of the tape during each circuitwithout rubbing the surface of the tape against a cleaning medium.

During the "run" mode, sensor 35 detects the "window" in the master tapeduring each complete pass. The controller 11A times the interval foreach pass and displays the information on display 14 alternately withthe number of passes completed.

To stop transporter 10, the operator has three choices. "Stop" switch 19is an emergency stop which will stop the tape in less than one second.In this case, the tape will usually not remain in its threaded path.Therefore, rethreading is necessary before restarting. When switch 19 isactivated, controller 11A disengages pinch rollers 67, 66 and 74 andremoves power from motors 60A, 62A, 70A and 80A. This allows the tape tobe quickly pulled down into vacuum columns 40 and 50, thus rapidlystopping it. Vacuum guide 76 provides some holdback tension to keep tapearound capstan 70, but all other guides become ineffective as the tapetension from guide 33 to capstan 60 drops.

Another method of stopping the tape is by activating "soft stop" switch20. When this switch is activated, the controller begins to reduce theaverage power applied to capstan 60. As the tape begins to slow, vacuumcolumns 40 and 50, by operation of the column transducers 48 and 56,respectively, command a corresponding reduction in the speed of motors62A and 70A. A tachometer (not shown) monitors capstan 60 and when aspeed of 200 ips or less is reached, the controller switches into thenormal "stop" routine. At this slow speed, the tape will remain threadedwithin the guides and capstans.

The third stopping method is called "cue stop" and is controlled byswitch 21. The "window" in the tape is usually placed at or near thesplice between the beginning and end of the tape. By detecting when thewindow passes sensor 35, the controller calculates the time which willpass before the window reaches sensor 35 again. If this time is greaterthan 15 seconds or less than 5 seconds when switch 21 is pressed, thetape is allowed to continue. When the window is within the predetermineddistance from sensor 35, the controller automatically goes into a "softstop" routine. Capstan 60 reduces tape speed down to 200 ips and thencontinues at that speed until sensor 35 detects the presence of thewindow. This signals the controller stop, leaving the window near vacuumcolumn 40 where it can be easily located.

PROCEDURE FOR UNLOADING MASTER TAPE

Once the tape has been stopped by using the "cue stop" switch 21, thewindow is located. The operator places an empty reel on hub 25. Afterthe splice is removed, the end of the master tape exiting the uppersection of bin 64 is threaded between pinch roller 66 and capstan 62,down into vacuum column 50, between pinch roller 67 and capstan 60,through sensor 36 and to the left of guide rollers 32 and 28. The tapeis wrapped clockwise around the reel on hub 25. The other end of thetape, that which has just exited bin 64, is placed so that it may bepulled back into the bin by the loading process without damage.

Then, mode switch 15 is placed in the "unload" mode and switch 17, whichcontrols the vacuum supply, is closed. Then the operator presses"start", the controller does a series of tests, as described above, toinsure the presence of vacuum, proper threading and that capstan 60 isnot rotating. If all conditions are valid, power is then applied tomotor 26 causing it to rotate clockwise. Vacuum column 50 pulls themaster tape down to the bottom of the column. This action creates aholdback tension of sufficient amount to provide good guidance aroundguide roller 28 and thus a good pack for storage of the master. When theend of tape passes sensor 36, the controller removes power from motor26.

An apparatus and method for controlling the speed and pack formation oftape in a high speed tape transporter is described above. Variousdetails of the invention may be changed without departing from itsscope. Furthermore, the foregoing description of the preferredembodiment according to the present invention is provided for thepurpose of illustration only and not for the purpose of limitation--theinvention being defined by the claims.

I claim:
 1. In a closed loop, high-speed tape transporter of the typewherein a closed loop of recording tape is passed across a pick-up headwhere a signal on the loop of tape is conveyed downstream to at leastone slaved duplicator, and wherein the loop of tape is conveyed from thepick-up head into a bin for accumulation ad storage while a trailinglength of the loop is passed across the pick-up head, and from the binback across the pick-up heads repeatedly whereby successive replicationsof the signal from the loop are conveyed from the pick-up head to theslaved duplicator, the improvement which comprises:(a) vacuum supplymeans; (b) the tape bin defining a tape deflecting surface opposite andin spaced-apart relation to an entrance through which the tape entersthe tape bin and against which said tape is propelled; and (c) aplurality of vacuum ports in vacuum flow communication with said vacuumsupply means and positioned in spaced-apart relation generally along thepath of tape movement on said tape deflecting surface to apply aprogressive braking force to the tape as it enters the bin and to slowthe tape speed and to cause the tape to form loops as it moves alongsaid tape deflecting surface, the loops assisting the tape to accumulatein the bin in a controlled manner.
 2. In a tape transporter according toclaim 1, wherein said tape deflecting surface comprises a curvedsurface, which curve begins at an angle acute to the direction of tapemovement into said bin and ends at an angle generally perpendicular tothe angle of tape movement into said bin.
 3. In a tape transporteraccording to claim 2, wherein said angle acute to the direction of tapemovement is 15 degrees.
 4. In a tape transporter according to claim 1,wherein said vacuum ports are equally spaced-apart.
 5. In a tapetransporter according to claim 1, wherein said vacuum ports define awidthwise dimension less than the width of the tape for being completelycovered as the tape moves along said tape deflecting surface.
 6. In atape transporter according to claim 1, wherein said tape deflectingsurface is defined by a polished, stainless steel wall of said bin. 7.In a tape transporter according to claim 1, wherein said ports arecircular.
 8. A method of reducing the speed of a moving tape comprisingthe steps of:(a) providing a structure defining a tape deflectingsurface against which the tape is propelled; and (b) providing aplurality of vacuum ports positioned in spaced-apart relation generallyalong the path of tape movement on the tape deflecting surface to applya progressive braking force to the tape as it is propelled against andalong the tape deflecting surface to slow the tape speed sufficiently tocause the tape to form loops as it moves along the tape deflectingsurface; said vacuum ports defining a widthwise dimension less than thewidth of the tape which is propelled against the tape deflectingsurface.
 9. A method according to claim 8, wherein said vacuum ports areprovided in equally spaced-apart relation.
 10. A method according toclaim 8, wherein said tape deflecting surface is defined by polishedstainless steel.